Fingerprints/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim is sleeping and snoring in his bed at night. Moby opens the door to Tim's room, drops down on all fours, and creepily crawls over to Tim's bed. He takes Tim's phone from the nightstand, and gently pulls Tim's hand closer to the phone in an attempt to unlock it with Tim's thumbprint. Tim wakes up. TIM: Huh? What are you doing?! Tim turns the bedside lamp on. MOBY: Beep. TIM: You are so addicted to that game. Moby jumps on the bed to sit next to Tim, trampling Tim's legs in the process. TIM: Ugh! Moby hands him a letter. Tim reads from the typed letter. TIM: Dear Tim and Moby, We were wondering, can two different people have the same fingerprints? From, Mrs. Marchese's Class. Well, it's possible… in theory. Like, maybe out of several hundred trillion people, you'd find two matching prints. An image shows a person standing below a large blue fingerprint. The screen splits to show rows of blue human silhouettes filling up the image on the other side. An animation scans along the rows of silhouettes until one of the silhouettes lights up in green. The blue fingerprint above the person on the right side turns the same color green, indicating a match. TIM: But, there are fewer than 10 billion people in the whole world. On the right side of the screen, many of the silhouettes in each row disappear, including the green silhouette. On the left side of the screen, the green fingerprint above the person's head turns back to blue. TIM: So, it’s pretty safe to say no two living humans have the exact same fingerprints. That's why they're such a useful way to identify people. The animation zooms in to show a close-up of the person with the fingerprint above his head. He holds up an ID card showing his photo, signature, and fingerprint. TIM: Fingerprints are the oldest form of biometric identification: a way to know who someone is using their physical characteristics. In ancient times, people used them to "sign" business agreements. And they're still one of the most convenient forms of personal identification. A three-way split screen shows animations of a finger being scanned on a doorknob display to open a door, a thumb being scanned on a car door display to unlock a car door, and Tim using his thumbprint to unlock his phone. TIM: Unlike a driver's license or passport, you can't exactly forget them at home. MOBY: Beep? TIM: No one knows exactly why people have fingerprints. We do know that they improve our sense of touch. Tim runs his hand over the fabric of his bedsheets. The animation zooms in to show his fingertip ridges. Vibration lines between the fingerprint ridges and the fabric appear. TIM: Running your fingertips over a surface creates tiny vibrations. This helps the nerves in fingertips feel even the finest textures. People used to think the raised lines of skin helped us grip objects. That's why they're called friction ridges. Tim grabs the glass of water on his nightstand. The animation zooms in to show his fingerprint ridges through the glass. TIM: But, it turns out that fingerprints actually reduce your grip on whatever we're touching. The water glass slips out of Tim's hand, almost falling on the bed before he catches it with both hands. TIM: Whoa! MOBY: Beep? TIM: Fingerprints develop while we're still in the womb. It's thought to be caused by one layer of skin growing faster than the other. The outermost layer of skin is called the epidermis. That's the part we see on our bodies. The epidermis itself has many layers. An animation shows a fetus in the womb sucking its thumb. A pop-out shows a zoomed in view of its fingertips on the cellular level. The pop-out expands to take up the entire screen, showing all the layers of the epidermis. TIM: The bottom one, the basal layer, is where new skin cells form. As a fetus develops, the basal cells are multiplying like crazy. But their space is limited by the layers of skin above them. With nowhere to go, the basal layer starts to buckle and twist. That forms the ridge patterns that make up fingerprints! An animation shows the cells in the basal layer multiplying, buckling more and more as the layers above them don't budge. Above the uppermost epidermal layer, an outline traces the ridge patterns that have formed. TIM: By the time a fetus is 24 weeks along, those patterns are locked in. An animation shows the fingerprints on the fetus's fingers as it sucks its thumb. MOBY: Beep? TIM: Well, fingerprints stretch as we grow, but their unique pattern stays the same. An image shows an infant holding up a finger with a distinct fingerprint. The pattern of the print remains the same as the infant morphs into an older child and then an adult. TIM: Even if you cut or injure your finger, the skin grows back with the exact same ridges. So, there's no way to change your fingerprints… not without doing a lot of damage, at least. That's why they can be so useful in police investigations. An animation zooms in on the fingerprint, as it is covered by yellow crime scene tape marked "Police Line Do Not Cross," which fills up the entire screen. TIM: Fingerprints have been used as evidence since at least the 1890s. An animation shows a police officer from the 1800s looking through a microscope. A page with several different fingerprints is on the table next to the microscope. TIM: That's when the patterns were officially categorized into loops, whorls, and arches. Fingerprints representing examples of each of the three types Tim mentions appear one by one above the police officer's head. TIM: Small details in the ridges, known as minutia, were also identified. These tiny differences are key to a fingerprint's uniqueness. An animation zooms in on the three example fingerprints, which now take up the entire screen. Labels representing the different types of minutia appear next to arrows pointing to each type on each fingerprint. TIM: Police began comparing prints found at crime scenes to those of suspects. If two prints had enough minutia in common, it was considered a match. And that meant that the suspect must have been at the scene. A split screen shows a fingerprint on the left side, and on the right side, an arrest record with a person's mug shot paper clipped to a file folder displaying images of his fingerprints. The fingerprint on the left side of the screen lights up in green as one of the fingerprints in the arrest record also lights up in green. The two green fingerprints merge into one large green fingerprint in the middle of the screen, indicating a match. MOBY: Beep? TIM: This same basic system is still in use today. The technology has advanced a lot since then. Improved imaging can show even tiniest minutia, including sweat pores and the exact width of a ridge. These make it easier to identify who a print belongs to. An animation shows a large 3D computer rendering of a fingerprint rotating in the middle of the screen. TIM: Instead of using messy ink and paper, prints can be scanned directly into a computer. The animation pulls back from the 3D print image to show that it's being displayed on a computer screen as a police officer scans a person's finger on a fingerprint scanning device. TIM: Local police departments can submit prints to the FBI. They've created a huge database of prints taken from crime scenes and arrest records from around the country. An animation shows a green fingerprint and a blue fingerprint on a computer display titled "Fingerprint Analysis." Below the prints, the text on the display reads "Browsing Database…" The blue fingerprint changes many times as the computer scans through the database looking for a match for the green fingerprint. The animation zooms out to show an FBI employee in front of the screen, surrounded by more screens. On the main screen, the computer stops scanning the blue fingerprints as one of them turns green and the text on the display reads "Match Found." TIM: Sophisticated programs can quickly identify possible matches. That helps narrow down suspects with much less work. MOBY: Beep? TIM: No, it's not as simple as it looks in those crime shows. Crimes scenes are covered in thousands of prints, one on top of the other. On rare occasions, they might be visible, like if they're in wet paint. But usually they're left behind by the sweat and oil in our skin. This invisible kind is called a latent print. An animation shows a black light being shined over a door, revealing several prints on the doorknob. The light moves up past the doorknob, revealing another print on the doorjamb. TIM: To save a latent print, investigators sprinkle it with a superfine powder that sticks to the oil. Then they can lift the image of the print with a special kind of tape, and transfer it to a card. An animation shows a brush applying fingerprint powder onto the print on the doorjamb. A piece of tape is placed on the print, lifting it and transferring it to a card. TIM: Most latent prints are too smudged to use. And many are left by people who didn't do anything wrong. A flashback animation shows a mail carrier delivering mail and leaning his hand against the doorjamb, in the exact location where the print was lifted. MOBY: Beep? TIM: Like, whoever lives there, or people who had a good reason for touching stuff at the scene. And it's not like you can just feed the collected prints into a computer and, boom, find a match. They have to be carefully cleaned up and then analyzed by experts. An animation shows the FBI employee in front of her many computer screens, digitally cleaning up a smudged print on the main screen. TIM: Even then, there might not be enough detail for a match. And experts might have different opinions on the same prints. Sometimes in a trial, it's left up to the jury to decide. An animation shows the FBI employee speaking in front of a jury from the witness stand of a courtroom, while holding up two posters with enlarged fingerprints on them and pointing to the various labeled minutia. TIM: Even if it's a match, that'll be just one of many pieces of evidence presented at the trial. It takes more than a fingerprint to prove someone's guilty of something. Like catching them red-handed with your property. Back in Tim's room, Moby is once again trying to unlock the phone with Tim's hand. Tim looks at him sternly. TIM: Stop that. Category:BrainPOP Transcripts